The input resistance of a common emitter transistor amplifier, if the output resistance is `500 kOmega`, the current gain `alpha=0.98` and the power gain is `6.0625 xx 10^(6)` is

Options

A. `198 Omega`
B. `300 Omega`
C. `100 Omega`
D. `400 Omega`

Answer

A

Explanation

Power gain = Current gain x voltage gain
Voltage gain , `A_(V) = beta(R_(2)/R_(1))`
Current gain `beta=alpha/(1-alpha) = (0.98)/(1-0.98) = 49`
`A_(V) = 49((500 xx 10^(3))/(R_(1)))`
Power gain, `R_(1)=6.0625 xx 10^(6)`
`49 xx ((500 xx 10^(3))/(R_(1))) xx 49 = 198 Omega`